Download Work, Power, and Energy Webquest

Work, Power, and Energy Webquest
Name ______________________________________
http://www.physicsclassroom.com/Class/energy/energtoc.html
Click on Lesson 1
Define the terms work, mechanical energy, potential energy, kinetic energy, and power.
Read the four examples in the box and determine which ones represent work and which
do not and then check your answer on the website above.
Which examples represent work?
Yes or No
A teacher applies a force to a wall and becomes exhausted.
Yes or No
A book falls off a table and free falls to the ground.
Yes or No
A waiter carries a tray full of meals above his head by one arm across
the room. (Careful! This is a very difficult question which will be
discussed in more detail later.)
Yes or No
A rocket accelerates through space.
What is the mathematical expression for WORK?
Read the three scenarios and explain how the angle Ө (theta) between F and d is:
Scenario A: Ө = 0 degrees –
Scenario B: Ө = 180 degrees –
Scenario C: Ө = 90 degrees –
What do the letters F and d stand for in these scenarios?
F–
d–
What are two units of measure for work?
1–
2–
Click on Click to continue the lesson on Work
Follow the directions for Diagrams A, B, and C. Write the equations and answers for
each diagram below:
Diagram A –
Diagram B –
Diagram C –
Click the NEXT >> button at the bottom of the page.
Read the section on Potential Energy.
What is the equation for gravitational potential energy?
What is the difference between gravitational potential energy and elastic potential
energy?
What is the equation for the elastic potential energy of a spring?
Click the NEXT >> button at the bottom of the page.
What is kinetic energy?
What is the equation for kinetic energy?
What is the unit of measure for kinetic energy?
Use the equation for kinetic energy to answer the following questions:
1. Determine the kinetic energy of a 1000-kg roller coaster car that is moving with a
speed of 20.0 m/s.
2. If the roller coaster car in the above problem were moving with twice the speed, then
what would be its new kinetic energy?
3. Missy Diwater, the former platform diver for the Ringling Brother's Circus had a
kinetic energy of 15 000 J just prior to hitting the bucket of water. If Missy's mass is 50
kg, then what is her speed?
4. A 750-kg compact car moving at 100 km/hr has approximately 290 000 Joules of
kinetic energy. What is the kinetic energy of the same car if it is moving at 50 km/hr?
(HINT: use the kinetic energy equation as a "guide to thinking.")
Click the NEXT >> button at the bottom of the page.
Define Mechanical Energy –
Is mechanical energy potential or kinetic energy?
List five examples of mechanical energy:
1–
2–
3–
4–
5–
Copy the diagram that illustrates the motion of Li Ping Phar. Include the numerical
values for PE and KE.
Click the NEXT >> button at the bottom of the page.
What are the equations for WORK and POWER?
WORK =
POWER =
What is the unit of measure for POWER?
What is another equation that describes POWER?
POWER =
Use the equations for WORK and POWER to answer the following questions:
1. Two physics students, Will N. Andable and Ben Pumpiniron, are in the
weightlifting room. Will lifts the 100-pound barbell over his head 10 times in one
minute; Ben lifts the 100-pound barbell over his head 10 times in 10 seconds.
Which student does the most work? Which student delivers the most power?
Explain your answers.
2. During the Personal Power lab, Jack and Jill ran up the hill. Jack is twice as
massive as Jill; yet Jill ascended the same distance in half the time. Who did the
most work? Who delivered the most power? Explain your answers.
3. A tired squirrel (mass of 1 kg) does push-ups by applying a force to elevate its
center-of-mass by 5 cm. Determine the number of push-ups which a tired squirrel
must do in order to do a mere 1.0 Joule of work. If the tired squirrel does all this
work in 4 seconds, then determine its power.
4. If little Nellie Newton lifts her 40-kg body a distance of 0.25 meters in 2 seconds,
then what is the power delivered by little Nellie's biceps?
5. Your monthly electric bill is expressed in kilowatt-hours, a unit of energy
delivered by the flow of l kilowatt of electricity for one hour. Use conversion
factors to show how many joules of energy you get when you buy 1 kilowatt-hour
of electricity.
6. An escalator is used to move 20 passengers every minute from the first floor of a
department store to the second. The second floor is located 5-meters above the
first floor. The average passenger's mass is 60 kg. Determine the power
requirement of the escalator in order to move this number of passengers in this
amount of time.
Use the following diagram to answer questions #7 - #9. Neglect the effect of friction and
air resistance.
7. As the object moves from point A to point D across the frictionless surface, the sum of
its gravitational potential and kinetic energies
a. decreases, only.
b. decreases and then increases.
c. increases and then decreases.
d. remains the same.
8. The object will have a minimum gravitational potential energy at point
a. A.
b. B.
c. C.
d. D.
e. E.
9. The object's kinetic energy at point C is less than its kinetic energy at point
a. A only.
b. A, D, and E.
c. B only.
d. D and E.
10. An object which weighs 10 N is dropped from rest from a height of 4 meters above
the ground. When it has free-fallen 1 meter its total mechanical energy with respect to the
ground is
a. 2.5 J
b. 10 J
c. 30 J
d. 40 J
11. During a certain time interval, a 20-N object free-falls 10 meters. The object gains
_____ Joules of kinetic energy during this interval.
a. 10
b. 20
c. 200
d. 2000
CHECK OUT THE ANIMATIONS ON EACH PAGE.